How are created folders in the contents folder of the USB Key ?

Hello,

I have a XDJ-R1, when I export mp3's via Rekordbox in my USB key, It will create folders in the Contents folder.

One folder for each artist and inside this folders, another folders for each album of each artist.

But some times, it creates folder named "UnknownArtist" or "UnknownAlbum".

I don't understand why because all informations about artist and album are filled in Rekordbox and It is display correctly on the XDJ-R1.

I would like to know how works the creation of this folders to understand why it does it ?

Thank you !

BR